Cutlass bearings have been the standard of use in several applications, some of which are marine and some of which are not. The typical marine application is journalling the propeller shaft of a fairly large boat or ship for rotation inside a stern tube. A typical non-marine application is journalling the driven shaft of a mud motor used to drill deviated or horizontal wells in the oil field.
A standard Cutlass bearing is a relatively long annular rubber member rotatably receiving a shaft through an opening in the center. The rubber member typically has slots or grooves on the interior surface to allow water to pass axially through the bearing to cool and lubricate it. The bearing typically includes a cylindrical metal sleeve secured in some fashion to the stern tube. The rubber member is typically bonded to the metal sleeve. Cutlass bearings have been used for decades in marine applications and have been used in mud motors for about as long as mud motors have been in existence.
Standard Cutlass bearings have a variety of disadvantages, some of which are remedied, or partially remedied, by reversing the situation, i.e. placing the rubber sleeve on the outside of the metal tube and fixing the metal tube to the shaft being journalled so the rubber sleeve rotates against the stern tube. Bearings of this general type have been proposed in the prior art as shown in U. S. Pat. Nos. 2,203,039; 2,348,274; 2,348,275; 2,380,715; 2,405,799; 2,538,921 and 5,143,455. It is this type device to which this invention most nearly relates.
Analysis of standard Cutlass bearings and reversed Cutlass bearings show they are defective in several respects.